In previous studies, we have demonstrated qualitative and quantitative differences in the oligosaccharides linked to glycoproteins of murine leukemia viruses of different host range classes. We will determine the precise number of glycosylation sites in ecotropic, xenotropic and dualtropic MuLV glycoproteins by analysis of tryptic glycopeptides using a high performance liquid chromatography separation procedure recently developed in our laboratory. The nature of the oligosaccharides linked to each glycosylation site will be investigated by gel filtration analysis of pronase digests, and determination of sugar composition by GLC analysis of trifluoracetate derivatives of methylglycosides. Immunoelectron microscopy will be used to investigate the cellular location of MuLV glycoproteins, including recombinant glycoproteins that are thought to be important in viral leukemogenesis. The mechanism by which gp70 is secreted into culture media in some MuLV infected cells will be investigated by kinetic analysis and comparison of the oligosaccharides of the secreted and membrane bound glycoprotein fractions. Ionophores and glycosylation inhibitors will be used to further define the factors which influence the intracellular transport of MuLV glycoproteins. Tacaribe virus, a member of the arenavirus group, will be used as a system for further studies of the structure and replication processes of this virus family. We will prepare cloned DNA copies of the viral genome RNA species, and use these in correlated studies of nucleic and protein sequences. We will identify all of the polypeptides coded by the Tacaribe viral genome, and investigate the processing events in their biosynthesis. We will characterize the mRNA species in Tacaribe virus infected cells, and use in vitro translation to determine the polypeptide products encoded by each mRNA. Hybrid arrest translation with specific restriction enzyme fragments of cloned DNA copies of Tacaribe genes will be used to map the locations of each major polypeptide.